The dash vent change has been discussed here several times over the
years. The change was made during the 1987 model year, meaning early 87
has the old cold air only dash end vents and later 87s have only air
that has passed through the heater core going the the end vents. The
change was made at serial number 13,413 of the 87 model year production,
pretty early on that year.

Mark
who prefers the cold air vent version but has 3 - 87s with the heated

Lee Peterson wrote:

>
> Mark, I was looking at my heater box last night.  I picked up a spare box to
> rebuild in my garage so that when it came time to do the replacement my
> vehicle would be disassembled for the shortest time possible.  I noticed
> something that might help you out.  I have an '89 and the spare box I picked
> up is also from a later van.  Sometime in the late 80's VW made a change in
> the heater system so that the vents at each end of the dash push heated air,
> not fresh air.  The top half of the heater box was changed so that the dash
> vent air supply comes out of the box on the heated side.  The spot on the
> unheated half of the box, where the dash vent hoses used to attach, is
> blanked off or I guess I should say it was never drilled out.
>
>..............